Acrosomal membrane

Abstract: Proteinaceous “Sperm Receptors” on the egg plasma membrane facilitate binding of sperm (Wolf et al., 1976). The inability of trypsin inhibitors to prevent binding of mouse sperm to eggs (Saling, 1981) suggests that acrosin activity is not required for gamete contact, but Ca2+ is necessary for sperm-egg contact in both hamsters (Yanagimachi, 1982) and mice (Saling, 1981).

Abstract: To identify novel human sperm membrane antigens, we analyzed two-dimensional gels of sperm extracts containing hydrophobic proteins that partitioned into Triton X-114. Four protein spots with isoelectric points (pIs) ranging from 4.5 to 5.5 and apparent molecular weights from 32 to 34 kDa were sequenced by mass spectrometry and found to contain common peptide sequences. Cloning the corresponding cDNA revealed that these protein spots were products of a single gene (SAMP32), encoding a protein of 32 kDa with a predicted pI of 4.57. SAMP32 has a potential transmembrane domain in the carboxyl terminus and is phosphorylated in vivo on serine 256. Northern blotting of eight human tissues and RNA dot blotting of 76 human tissues showed that SAMP32 expression was testis specific. SAMP32 contained an amino terminal domain homologous to the major malarial circumsporozoite surface protein and a domain similar to that of Krp1 from Schizosaccharomyces pombe in its carboxyl terminus. The SAMP32 locus consists of seven exons on chromosome 6q15-16.2. Antiserum against recombinant SAMP32 recognized protein spots originally cored from a two-dimensional gel. This antiserum strongly stained the equatorial segment and faintly stained the acrosome cap of ejaculated human spermatozoa by immunofluorescence. Immunoelectron microscopy showed that SAMP32 was associated with the inner acrosomal membrane in the principal and the equatorial segments of the sperm acrosome. By immunostaining enzyme-dissociated testicular cells, SAMP32 was localized to Golgi phase round spermatids and subsequent stages of acrosome biogenesis. Recombinant SAMP32 reacted with serum from an infertile man, suggesting that it is isoantigenic. Antibodies against recombinant SAMP32 inhibited both the binding and the fusion of human sperm to zona-free hamster eggs.

Abstract: The antioxidant systems of superoxide dismutase (SOD), catalase (CAT), reduced glutathione (GSH), and glutathione peroxidase (GSH-Px) are important in maintaining sperm motility and viability. The purpose of this study was to determine the effects of varying doses of trehalose on in vitro semen quality variables and antioxidant activities of frozen-thawed bovine semen. The semen samples, diluted with an extender containing trehalose (0, 25, 50, 100, and 200 mM), were evaluated. The extender supplemented with 100 mM trehalose exhibited the greatest percentages of sperm motility, acrosomal membrane integrity, and plasma membrane integrity in comparison with the control group (P 0.05). Extender supplemented with trehalose did not affect SOD levels. Compared with the other groups, CAT was greater with the supplementation of trehalose at 100 and 200 mM (P < 0.05). The extender supplemented with trehalose had enhanced GSH-Px activity compared with the control group (P < 0.05). However, increasing the doses of trehalose (100, 200 mM) decreased GSH-Px activity, compared with 50 mM trehalose (P < 0.05). Compared with the other groups, trehalose at the concentration of 25 and 50 mM increased GSH activity (P < 0.05). The application of 200 mM trehalose produced the least amount of GSH activity among all of the groups (P < 0.05). In conclusion, extender supplemented with trehalose reduced the oxidative stress induced by freeze-thaw and improved measures of bovine semen quality. The antioxidant characteristics of trehalose may be related to its effectiveness in membrane cryopreservation. Further studies are required to obtain more concrete results on the determination of lipid peroxidation and antioxidant capacities of trehalose in cryopreserved bovine semen.